Darryl Greenamyer set a world's absolute speed record with this modified Bearcat - 483 mph.
The Bearcat was designed to replace the F6F. First prototype appeared Aug 44; two months later Navy ordered a large number. Although never used in combat by US, more than 24 squadrons of -1s reached Navy after WWII while waiting for first jets to enter service. -2 built 1948, was more powerful and generally improved over -1. Of 305 built, 12 were night fighter variants and 30 were photo-recons. Were used by French in Indochina and by Royal Thai and Burmese air forces. Conquest I modified by Darryl Greenamyer for unlimited racing, winning many major events and the Reno Air Races 6 times. Set closed course record 1975 of 435 mph (since exceeded) and absolute speed record for propeller aircraft of 483 mph, 1969; latter flight required 2-way pass over 3 km straight course. (Another F-8F, Rare Bear, set new speed record of 528 mph at Las Vegas NM. during summer 90.) Aircraft mods included shortened wings (normal span of 35 ft 10 in reduced to about 27.5 feet), special aerodynamic fillets, and special attention to surface smoothness. Hydraulic systems and all unnecessary components removed except for essential flight and engine instruments. Hydraulic gear system replaced for racing with lighter 1-shot nitrogen system which retracted the gear; gravity lowered it. Water-boiling system used for oil cooling. Engine is modified R2800 with specially made front cover built to accept oversize propeller (from a Skyraider). Prop size leaves little ground clearance and makes 3-point landings and takeoffs a must. Aircraft flown to Washington from west coast in modified form without even a compass and a range of only 400 miles. On this trip, gear did not fully retract. In addition, streamlined racing canopy allowed little downward visibility; trip was a real adventure. Greenamyer was Lockheed test pilot who has flown SR-71 and YF-12. Assembled only privately-owned F-104 from engineering and crash parts. Although he set world's record of just over 1000 mph in 1-04, was denied FAI approval due to recording equipment failure (record had to be set over 3 km measured course at under 1000 ft altitude).
ADDENDA TO F8F "CONQUEST I"
(EXTRACTED FROM "SPORT FLYING" BY EDITORS OF FLYING MAGAZINE, SCRIBNER'S SONS)
Armor and armament already removed from N1111L. Greenamyer's team removed large, stock bubble canopy and replaced it with a much smaller one scrounged together out of odd parts--some of them from a P3A.
Original 185-gal bag-type fuselage fuel tank (located between front and rear wing spars beneath pilot) removed, and entire compartment was caulked with integral tank sealant, bringing capacity up to 310 gals. (Part of wing sealed as well, with intention of flying plane in a transcontinental race, but plan never carried out.) Airplane nose-heavy from removal of radio and radar equipment originally placed behind pilot.
First, wings clipped. Easy job since F8F equipped with breakaway wing tips. 42-in outer panel of each wing separately skinned and held to inner portion of wing with bolts designed to fail at a lower load than that at which inner section of main spar would fail. If pilot pulled excessive g-loads in combat, outer wing panels would separate, protecting inner wing from failure. Straps had been installed to cover breakaway seam in skin; these were detached, the bolts undone and wing tips removed, reducing span to about 27.5 feet. Special racing tips designed by Mel Cassidy, Lockheed aerodynamicist, and fabricated in sheet aluminum.
Original Bearcat equipped with slotted flap of fabric and metal construction with hinges protruding below lower surface of each wing. These flap hinges removed, fabric skins stripped off and sheet metal covering of wing extended with hinges protruding below lower surface of each wing. These flap hinges removed, fabric skins stripped off and sheet metal covering of wing extended continuously to trailing edge.
Crude bubble canopy replaced with tiny, smooth, Formula One canopy of molded Plexiglas in which there was barely room for Greenamyer's head to turn from side to side. Integral fuselage tank, which had developed leaks because of relative movement of its parts under flight loads, resealed. An external strap, running most of length of underside of main spar and protruding about a quarter of an inch, faired with balsa wood.
Entire electrical system removed from aircraft. All instruments direct- reading, and a 15-volt dry-cell battery was carried in cockpit to power gear warning lights and radio. Engine started with ground power controlled by external switch panel which was disconnected once engine was running. Electric auxiliary fuel pump replaced with hand wobble pump.
Hydraulic system also went; only main cylinders on landing gear retained; a small (about 5 in diameter and 20 in long) nitrogen bottle installed to activate gear. Charged with nitrogen at 1900 psi, bottle good for 1 raising of gear. Gravity used to lower. Gear made to retract very rapidly--less than 5 seconds--because thought Unlimited races might use race-car start, but proved not to be the case.
Wing root leading-edge air intakes for oil cooler and carburetor sealed with sheet-metal fairings. In order to eliminate aerodynamic drag of oil cooler, was immersed in 24-in boiler filled with ADI (anti-detonant injection) mixture of alcohol and water which was fed into cylinders at manifold pressures exceeding 50 inches. This boiler, which underwent a number of mods and relocations in development of the airplane, originally placed ahead of firewall and vented through small hole in front of the cockpit on left side of fuselage. Boiler, with capacity of 7-10 gallons, boiled off about 35 of the 60-75 gallons of ADI used by airplane in a race. (Use of water boiler for cooling had been one modification incorporated in Bf-209 that had bettered 469 mph 1939.)
-30W engine replaced with R-2800-83A, takeoff rating of 2100 hp. In place of updraft carb of -30W, -83A equipped with downdraft carb. Iintake duct constructed to run up behind engine and over rear row of cylinders--breathed air from under the cowling that had passed over top of the first row. Cowl flaps, located on upper rear edge of cowling, bolted in shut position, leaving only small slot for release of cooling air.
Stock F8F prop replaced with one from Douglas AD-1 Skyraider; had diameter of 13 ft 6 in and weighed 425 lbs. Since prop was some 11 in larger than stock one, and Bearcat was rather critical in prop clearance to start with, N1111L had to be taken off and landed in 3-point position. In level attitude, prop would have hit ground. Engine nose replaced with R-2800-44 type--low prop-speed gearing with a prop/crankshaft ratio of .35:1, giving prop speed of 980 rpm at normal engine speed of 2800 rpm and tip speed of nearly 700 mph at 400 knots.
Originally spinnerless, plane fitted with spinner from P-51H Mustang. At other end, blunt tip of tail cone, from which arrester hook had extended, faired over with what looked like pointed stinger. Stinger later knocked off when plane jumped chocks and broke tie-down chain during full-power run- up. New stinger with sharp, straight upper edge installed in its place.
Spring 66, new boiler made, containing 2 oil coolers in place of 1, and installed in lower part of fuselage behind cockpit. Integral fuel tank, which was leaking again, resealed.
Stainless steel slippers installed on upper and lower surfaces of horizontal tail to close elevator gaps, and aileron gaps sealed with Ceconite. In attempt (later proved ill-advised) to reduce wetted area, upper 28 in of vertical tail clipped off.
-83 supercharger replaced with CB-17 type (used on DC-6, Convair, and other multi-engined craft), boosting maximum power to 2,500 hp--at some expense in reliability, however, because power section was still less beefy -83A type. Low-tension ignition system installed. After-spinner fairing from Constellation inserted behind prop, covering engine nose case and inner lips of cowling, which simply stopped in a smooth contour over cylinder.
At this point, Smirnoff Vodka offered sponsorship to Greenamyer, and plane was at alast painted--white with blunt-nosed blue arrows on fuselage and wings. With painting, entire skin filled and smoothed, and elevator gap seals-- which proved to impair longitudinal stability--were removed.
At 1966 Los Angeles Air Races at Lancaster CA, Greamyer made first assault on piston speed record. Stubby, avocado-shaped Bearcat, deprived of much of its vertical tail area and aspect ratio, tried to fly sideways if Greenamyer took feet off rudder pedals. Speed record attempt abandoned. Having borrowed stock tail assembly from Bill Fornof, owner of a familiar copper-and-black unmodified Bearcat, Greenamyer won Reno '66 with usual ease. Before the 1967 Reno races, equipment for the injection of nitromethane and water was installed. Greenamyer flew plane from Las Vegas to Edwards AFB Aug 68 for another attempt at world record speed. En route, newly installed cockpit canopy split along side and its after-edge rose 7 in upwards; crack stopped, however, sparing Greenamyer inconvenience of having head scooped off as canopy darted backwards. At Edwards, broken canopy replaced with original one, which had been polished back to its transparency (had been sandblasted in storm while parked at Reno) by its maker, and plane was ready for record.
No luck. During preparatory run at 500 mph, a piston blew--probably because of sand damage. Piston and cylinder replaced following week; but rebuilt engine seized during warmup and was ruined.
Greenamyer borrowed R-2800 CA-18 engine from Aircraft Cylinder Inc., Sun Valley CA engine-maintenance firm. Using same -44 nose case and Skyraider prop and essentially same supercharger as -83A engine, went to Reno and won again--this time running only 2 mph faster than Chuck Hall, whose P-51 Mustang turned unusually high 386 mph on final heat.
Conquest I returned to Vegas for the winter.
Bill Fornof wanted his tail back. Greenamyer's crew accordingly spent winter building up old vertical tail to original height and installing enlarged dorsal fin after consultation with Grumman. At last, constructed 3 welded aluminum fuel tanks (after integral fuel tank had badly deteriorated) and installed them in fuselage compartment; thereafter, no trouble with fuel leakage.
Greenamyer acquired pistons and cylinders of CB-17 type and installed them in CA-19 crankcase from borrowed engine; to this power section, attached overhauled blower from old engine--a CB-17 type to start with--and old -44 nose section. In Jul 69 had a complete CB-17 engine with exception of -83 crankcase; that is, he had CB-17 power plus airline reliability. Back at Edwards for new speed record attempt, landing gear doors that previously had been opening a half inch or so at high speeds (because of pressure difference between outside and inside of wing) were fitted with backward-facing airscoops to vent overpressure.
Grumman again consulted on subject of exhaust blast which was directed outward from fuselage, leaving a stain over a wide area of wing trailing edge. To narrow exhause wake, extensions lying flat against sides of the fuselage added to exhaust pipes, and cuff installed to cover exhaust roots where they emerged from beneath cowling. After test flight, was apparent that fuselage sides might suffer from exposure to 600 exhaust, and a stainless steel shield 5 ft long was riveted to fuselage side along exhaust path. Behind it, however, white paint blistered all the way to tail.
16 Aug, plane flown 4 times along Edward's 3-km course--with appropriate official timers--and world record speed of 483.041 mph established. On best run, Greenamyer indicating about 510 mph, turning 3000 rpm, and pulling 75 inchses with nitromethane injection.
During record flight, Greenamyer subject to cockpit temperatures of about 200; he suffered burns on his hands traced to exhaust leaks from coupling beneath cowling; hot exhaust was flowing out of cowl-flap slots and into small ventilating louvers on canopy frame. Exhaust stains actually found on inside of frame. Cause of exhaust leak was increased exhaust back pressure caused by extensions; since nothing could be done about it, Greenamyer strapped icepack to his chest on which to cool his hands while flying. Cockpit had never been a hospitable place to start with; ram effect alone raised temperature of 100 desert air to 140 as it entered cockpit, and air was also full of fumes which unaccountably found their way into cockpit from oil- cooler boiler. Greenamyer breathed through oxygen mask while flying the airplane.
In final form, "Conquest I" was tall, flat, stub-winged airplane with empty weight of 5800 pounds, of which 2300 pounds was big DC-6 engine. Power loading racing trim less than 3 lbs/hp; fuel consumption at full power on order of 300 gals/hr. Instrumentation normal with addition of torque pressure gauge reading horsepower directly in form of oil pressure. During record run, Greenamyer read 3200 hp. Greenamyer attributed success to strategy of modifying airframe for min drag while keeping engine more or less stock-- unlike majority of other racers who ran highly tweaked engines in stock or nearly stock airframes. Takeoff power rating of CB-17 engine in DC-6, he points out, is only 3 inches lower that that which he used at Reno with same rpm.